What was found
DURING A TRAINING FLIGHT THE PILOT ATTEMPTED TO EXTEND THE GEAR & HAD THE 5 AMP LG CONTROL CB POP. THE PILOT EXTENDED THE GEAR USING THE NITROGEN BLOW DOWN SYS IAW THE POH & AFM, THE GEAR WAS DOWN & LOCKED WITH 3 GREEN INDICATIONS. THE SYS WAS TROUBLE SHOT & DUPLICATED ON THE GND, A WIRE OFF THE RT MLG UPLOCK SWITCH WAS GROUNDING OUT IN THE RT WING CAUSING THE PROBLEM. THE WIRING WAS REPAIRED, SECURED GEAR & CYCLED 15 TIMES. BLOW DOWN BOTTLE SERVICE & RETURNED TO SERVICE.